Drainage network reorganization affecting the Nene and Welland catchments of eastern England as a result of a late Middle Pleistocene glacial advance

Abstract Britain's latitude is critical for determining the southerly extent of western European ice sheet expansion. Palaeoclimate and palaeosea‐level reconstruction in Britain, however, is complicated by spatially discontinuous glacigenic deposits and genetic and stratigraphic interpretations have relied on their lithological characteristics. This study adopted a sedimentary facies approach combined with geomorphological analyses for investigating upper Middle Pleistocene deposits in two adjacent catchments: Nene and Welland. Detailed sedimentology determined not only genesis of ice‐contact (Welland) and glaciolacustrine (Nene) deposits but also provided insight on lake surface water levels. The ice‐contact deposits recorded a constant lake level at the same height as alluvial remnants upstream in the Welland valley. These alluvial remnants are located where present tributaries join the Welland, indicating they were formed where influent streams entered a former lake and therefore can be interpreted as fluvial terraces resulting from local baselevel rise. The glaciolacustrine deposits in the Nene valley recorded fluctuating lake levels, indicating that altitudinally separated sand and gravel bodies coincident with these fluctuations and located where influent streams entered the lake also can be interpreted as fluvial terraces, but resulting from fluctuating baselevel. Sand and gravel bodies at the southern end of a dry valley linking the two catchments are interpreted as alluvial fan remnants, and those occurring on interfluves downstream of the alluvial fan remnants as flood deposits emanating from lake overflow. This drainage reorganization probably occurred in marine oxygen isotope stage (MIS) 8, but the ice advance footprint is different to that in MI 6.